Megger-Insulation Resistance Tester

What is Megger?

Insulation resistance IR quality of associate electrical system degrades with time, surroundings condition, i.e., temperature, humidity, wet and dirt particles.

It conjointly gets compact negatively because of the presence of electrical and mechanical stress, therefore it’s become terribly necessary to see the IR (Insulation resistance) of apparatus at a relentless regular interval to avoid any live fatal or unconditioned reflex.

Uses of Megger

The device alter U.S. to live electrical leak in wire, results ar terribly reliable as we have a tendency to shall be passing current through device whereas we have a tendency to ar testing. The instrumentation essentially uses for verificatory the electrical insulation level of any device like motors, cables, generators, windings, etc. this can be {a terribly|a really|a awfully} well-liked check being administered since very long back. Not necessary it shows U.S. precise space of electrical puncture however shows the number of leak current and level of wet at intervals electrical equipment/winding/system.

History of Megger

The device is being employed since 1889, quality raised throughout Twenties since the long back device is same in its uses and purpose of testing, few real enhancements appeared in recent years with its style and quality of tester. currently high-quality choices ar on the market that ar simple to use and quite safe.

Types of Megger

This can be separated into chiefly 2 categories:-

1.            Electronic sort (Battery Operated)

2.            Manual sort (Hand Operated)

But there's another forms of megger that is motor operated sort that doesn't use battery to provide voltage it needs external supply to rotate a electrical motor that successively rotates the generator of the megger.

Electronic sort Megger

Important parts:-

1. alphanumeric display:- A alphanumeric display to indicate IR price in digital kind.

2.Wire Leads:- 2 nos of wire leads for connecting megger with electrical external system to be tested.

3.choice Switches:- Switches use to pick out electrical parameter ranges.

4. Indicators :- To indicates varied parameters standing i.e.                   On-Off. for instance Power, hold, Warning, etc.

Note: – higher than construction isn't similar for each megger, it distinction seems manufacture to manufacture however basic construction and operation ar same for all.

Advantages of Electronic sort Megger

• Level of accuracy is incredibly high.
• IR price is digital sort, simple to browse.
• One person will operate terribly simply.
• Works utterly even at terribly full area.
• Very handy and safe to use.

Disadvantages of Electronic sort Megger

• Require associate external supply of energy to energies i.e.               Dry cell.
• Costlier in market.

Hand Operated Megger

Important parts:-

Analog show:- Analog display provided on front face of tester for IR worth recording.

Hand Crank:- Hand crank wont to rotate helps to attain desired rev needed generate voltage that runs through electrical system.

Wire Leads:- Used same as in electronic tester i.e. For connecting tester with electrical system.

Advantages of Hand Operated Megger

• Still keeps vital in such advanced world as it’s AN oldest           technique for IR worth determination.

• No external supply needed to control.

• Cheaper offered in the market.

Disadvantages of Hand Operated Megger

• a minimum of a pair of person needed to control i.e. one             for rotation of crank alternative to attach megger with                  electrical system to be tested.

• Accuracy isn't up to the amount as it’s varies with rotation of crank.

• need terribly stable placement for operation that could be          a very little exhausting to search out at operating sites.

• Unstable placement of tester might impact the results of tester.

• Provides AN analog show result.

• need terribly high care and safety throughout use of constant.

Construction of Megger

Circuit Construction options :-

1. Deflecting and management coil : Connected parallel to the generator, mounted at right angle to every alternative and maintain polarities in such how to created torsion in other way.

2.  Permanent Magnets : manufacture field of force to deflect pointer with North-South pole magnet.

3. Pointer : One finish of the pointer connected with coil another finish deflects on scale from time to zero.

4. Scale : A scale is provided in front-top of the megger from vary ‘zero’ to ‘infinity’, change North American nation to scan the worth.

5. D.C generator or Battery affiliation : Testing voltage is created by hand operated DC generator for manual operated Megger. Battery / electronic voltage charger is provided for automatic kind Megger for same purpose.

6. Pressure Coil Resistance and Current Coil Resistance : shield instrument from any harm as a result of low external ohmic resistance.

Working Principle of Megger

•   Voltage for testing created by hand operated megger by rotation of crank just in case of hand operated kind, A battery is employed for electronic tester.

• 500 potential unit DC is decent for playacting take a look at on instrumentality vary up to 440 Volts.

• 1000 V to 5000 V is employed for testing for prime voltage electrical systems.

• Deflecting coil or current coil connected serial and permits flowing the electrical current taken by the circuit being tested.

• The management coil conjointly referred to as pressure coil is connected across the circuit.

• Current limiting electrical device (CCR and PCR) connected serial with management and deflecting coil to shield harm just in case of terribly low resistance in external circuit.

• In hand operated megger magnetic attraction induction impact is employed to provide the take a look at voltage i.e. coil arranges to maneuver in permanent field of force or the other way around.

• Where as in electronic kind megger battery area unit wont to manufacture the testing voltage.

• As the voltage will increase in external circuit the deflection of pointer will increase and deflection of pointer decreases with a will increase of current.

• Hence, resultant torsion is directly proportional to voltage and reciprocally proportional to current.

• When electrical device being tested is open, torsion because of voltage coil are most and pointer shows ‘infinity’ means that no shorting throughout the circuit and has most resistance at intervals the circuit below take a look at.

• If there's tangency pointer shows ‘zero’, which implies ‘NO’ resistance at intervals circuit being tested.

Work philosophy supported ohm-meter or ratio-meter. The deflection torsion is created with megger tester because of the field of force created by voltage and current, equally like ‘Ohm’s Law’.

The torsion of the megger varies in an exceedingly ration with V/I, (Ohm’s Law:- V = IR or R = V/I). ohmic resistance to be measured is connected across the generator and serial with deflecting coil.


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